1. Field of the Invention
The present invention relates to a two-layered TAB (Tape Automated Bonding) package which includes a conductive pattern and a flexible base material. More particularly, the invention relates to the TAB package which is capable of packaging a semiconductor chip thereon and connecting a printed circuit board or the like.
The present invention relates to a liquid-crystal panel unit using the TAB package.
2. Description of the Related Art
The inventors of the present invention know that the TAB package has been made to have a tape-like insulated flexible base material allowing a chip to be packaged thereon. The flexible base material contains conductive patterns for connecting the chip to a printed circuit board or the like. The insulated flexible base material normally employs polyimide or polyester as its material.
When the TAB package is used for composing a liquid-crystal panel unit having a liquid-crystal panel and a printed circuit board connected therewith, the TAB package is designed to package a chip of liquid-crystal-driving LSI (Large Scale Integrated Circuit) on itself for the purpose of connecting the liquid-crystal panel to its relevant printed circuit board.
For reducing the liquid-crystal panel unit in size, the region of the conductive patterns included in the TAB package are bent so that the tips of the conductive patterns, that is, the outer leads are allowed to be connected to the electrodes of the liquid-crystal panel.
As mentioned above, the foregoing TAB package includes the flexible base material on which a packaging area for packaging the chip of the liquid-crystal-driving LSI. The conductive patterns for connecting the chip to the liquid-crystal panel and the input-side outer leads for connecting the chip to the printed circuit board are formed lengthwise on the flexible base material.
In actual arrangement, the liquid-crystal panel is connected to the printed circuit board for composing the liquid-crystal panel unit by using the TAB package having the chip of the liquid-crystal-driving LSI packaged thereon. In packaging operation, the tips of the conductive patterns, that is, the output-side outer leads are connected to the electrodes of the liquid-crystal panel. Then, the region of flexible base material on which the conductive pattern is formed is bent so that the packaging area for packaging the chip is opposed to the conductive patterns. It results in the input-side outer leads being connected to a conductive pattern of the printed circuit board.
The flexible base material included in the TAB package generally has a thickness of 50 .mu.m to 125 .mu.m and high stiffness. The thickness and characteristic indicate that the bent flexible base material is likely to be restored to an original, that is, horizontal state. For soldering the liquid-crystal panel to the printed circuit board, therefore, it is necessary to bend the flexible base material and keep the bending state. This is troublesome work.
Hence, the aforementioned TAB package has inferior soldering workability. Further, the relatively large stress of the flexible base material may cause the soldered connection to be broken, thereby damaging the connection between the liquid-crystal panel and the printed circuit board. It results in disadvantageously lowering reliability of the connection.